1. Field of the Invention
The present invention relates to a non-volatile semiconductor memory suitable for high integration, and more particularly to a non-volatile semiconductor memory capable of performing electrical writing and erasure which is characterized by electron injection from a source side.
2. Description of the Prior Art
Referring to a conventional non-volatile semiconductor memory shown in FIG. 5, an N-type drain region 21 and an N-type source region 22 are provided on the surface of a P-type semiconductor substrate 20. A three-layer film 27 is provided apart from the source region 22 by a constant distance. The three-layer film 27 includes a floating gate 23, a layer insulation film 24 and a control gate 25. A side wall electrode 26 is formed on the three-layer film 27. With the above-mentioned structure, the optimum potentials are applied to the side wall electrode 26 and the control gate 25, respectively. As a result, electrons can be injected to the floating gate from the source side.
Referring to the conventional non-volatile semiconductor memory, a side wall portion 26 is formed on the three-layer film 27 having the floating gate 23 on a self-control basis and is used as an electrode. Consequently, the whole manufacturing steps are very complicated.
Furthermore, the side wall portion 26 is also used for wiring. In this case, wiring resistance is increased so that signals are delayed. Accordingly, the side wall portion 26 can be used only in situations where a delayed signal response can be tolerated.
It is an object of the present invention to provide a non-volatile, large capacity, high speed semiconductor memory capable of performing electrical writing and erasure that is easy to manufacture and permits electron injection from a source side.